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In the troy pound, fuppofing the quantity of water to amount 

 to loo grains, the quantities of the three earths will be, 



Hence we fee that in the drier countries, where the fall of rain 

 IS but 20 inches, the foil, to be fertile, muft be clofer, and the 

 quantity of calcareous earth much increafed, and that of the fili- 

 ceous much diminifhed. Thus, in the climate of Turin, where 

 the fall of rain exceeds 40 inches, the proportion of filiceous earth 

 is from 77 to 80 per cwt. and that of calcareous from 9 to 14, 

 to fufFer this excefs of rain more eafily to evaporate. In the cli- 

 mate of Upfal, where the fall of rain is 24 inches, the proportion 

 of filex is only 56 per cwt. but that of calx is 30 ; and in the 

 climate of Paris, which is ftill drier, the proportion of filex is 

 only from 46 to 51, and that of calx 37,5 per cwt. and hence we 

 may perceive the neceffity of attending to the average quantity 

 of rain to judge of the proper conftitution of fertile lands on 

 fixed principles. The quantity of rain differs much in different 

 parts of the fame kingdom, but in general in Ireland I believe it 

 to be between 24 and 28 inches on an average. 



In 



